There is a joke about that here. Ahem.
A guy with no arms enters a bar and asks where the bathroom is. He enters the bathroom and asks one of the men inside:
"Sir, could you help me, you know, I have no arms..."
The man helps and after he tucks it back and zips the fly, he asks:
"Umm...not to be rude, but why is your penis so green and sticky?"
The man then reveals both of his arms under his clothes and says:
"I don't know, and that's why I'm not touching it!"